Turbulent stress measurements downstream of three bileaflet heart valve designs in pigs

Objective: Mechanical heart valves can cause thromboembolic complications, possibly due to abnormal flow patterns that produce turbulence downstream of the valve. The objective of this study was to investigate whether three different bileaflet valve designs would exhibit clinically relevant differences in downstream turbulent stresses. Methods: Three bileaflet mechanical heart valves (Medtronic Advantage^®, CarboMedics© Orbis™ Universal and St. Jude Medical^® Standard) were implanted into 19 female 90 kg pigs. Blood velocity was measured during open chest conditions in the cross sectional area downstream of the valves with 10 MHz ultrasonic probes connected to a modified Alfred^® Pulsed Doppler equipment. As a measure of turbulence, Reynolds normal stress (RNS) was calculated at three different cardiac output ranges (3–4, 4.5–5.5, 6–7 L/min). Results: Data from 12 animals were obtained. RNS correlated with increasing cardiac outputs. The highest instantaneous RNS observed in these experiments was 47 N/m², and the mean RNS taken spatially over the cross sectional area of the aorta during systole was between 3 N/m² and 15 N/m². In none of the cardiac output ranges RNS values exceeded the lower critical limit for erythrocyte or thrombocyte damage for any of the valve designs. Conclusions: Reynolds normal stress values were below 100 N/m² for all three valve designs and the difference in design was not reflected in generation of turbulence. Hence, it is unlikely that any of the valve designs causes flow induced damage to platelets or erythrocytes.     

Plasma Norharman (β-Carboline) Levels are Elevated in Chronic Alcoholics

Based on the hypothesis that condensation products of neurotransmitters with aldehydes are involved in the pathogenesis of alcoholism, aromatic beta-carbolines (norharman and harman) were measured in the blood plasma of alcoholics and nonalcoholics. The identity of the extracted compounds was confirmed by various elution conditions of the high performance liquid chromatography (HPLC), newly developed radioreceptor assays, and the mass spectrum of norharman. The levels of norharman and harman in nonalcoholics were unchanged after a load with ethanol (1 g/kg body weight). The norharman levels of the alcoholics were significantly higher than that of the nonalcoholic controls (99.5 +/- 26.6 pg/ml vs. 26.9 +/- 10.7 pg/ml; p less than 0.001) and did not change significantly during a 3-week detoxication period. In the subgroup of alcoholics with delirium or hallucinosis, a slight increase of norharman during detoxication could be detected while in alcoholics with vegetative withdrawal symptoms norharman levels dropped slightly over time (p = 0.07). No difference was found with respect to harman between nonalcoholics and alcoholics. These results suggest disturbed regulatory processes in the formation and/or metabolism of norharman in alcoholics. Further investigations are needed to reveal a possible marker function of norharman in alcoholic patients.     

Berufsbedingte Hauterkrankungen—Paradigma der Sekundärprävention

The dermatologist's procedure was introduced in 1972 by employers' liability insurance funds in the industrial, agricultural and public sectors of Germany's statutory occupational accident insurance as a "procedure for early detection of occupational skin diseases". So far, it is still the most relevant tool for secondary prevention in occupational dermatology in Germany. According to the intention of this procedure, insured persons with a skin disease in which an occupational aetiology is suspected must be offered preventive measures and, if necessary, given appropriate treatment to avoid their losing their jobs. On the initiative of the Central Federation of Industrial Professional Associations (HVBG), a study group was set up in 1999 from among its membership in cooperation with the Working Committee of Occupational and Environmental Dermatology (ABD) and the Professional Organisation of German Dermatologists (BVDD) to improve on the efficiency of the "classic" dermatologist's procedure. The proposed "optimised" dermatologist's procedure is based on the assumption that early detection followed by competent and intensified skin protection and skin care will be successful in retarding or stopping the progression of occupational dermatoses, while later treatment is likely to be less effective. In October 2002, a pilot study started in Northwest Germany to establish by scientific evaluation whether the implementation of secondary protective measures is definitively better when the provisional "optimised" dermatologist's procedure is followed. The study results should allow detailed suggestions for an improved dermatologist's procedure before it is introduced nationwide.     

Neurobehavioral effects among subjects exposed to high static and gradient magnetic fields from a 1.5 Tesla magnetic resonance imaging system--a case-crossover pilot study.

The interactive use of magnetic resonance imaging (MRI) techniques is increasing in operating theaters. A study was performed on 17 male company volunteers to assess the neurobehavioral effects of exposure to magnetic fields from a 1.5 Tesla MRI system. The subjects' neurobehavioral performances on a neurobehavioral test battery were compared in four 1-hr sessions with and without exposure to magnetic fields, and with and without additional movements. Adverse effects were found for hand coordination (-4%, P < 0.05; Pursuit Aiming II) and near visual contrast sensitivity (-16% and -15%, P < 0.10; Vistech 6000). The results from the remaining tests were inconclusive due to a strong learning effect. No additional effect from gradient fields was detected. The results indicate that working near a 1.5 Tesla MRI system may lead to neurobehavioral effects. Further research is recommended, especially in members of operating teams using interactive MRI systems.     

Receptor binding of N-(methyl-11C) clozapine in the brain of rhesus monkey studied by positron emission tomography (PET)

By means of positron emission tomography the uptake and kinetics of N-(methyl-¹¹C)clozapine in different brain regions have been studied in Rhesus monkeys. ¹¹C-clozapine rapidly entered the brain and maximum radioactive uptake was seen 5–12 min after administration. Highest uptake was measured in the striatum. Other regions with an uptake higher than in the cerebellum were thalamus and mesencephalon. The radioactivity from different brain regions decreased with an elimination half-life of about 5 h and parallelled the plasma kinetics of unlabelled clozapine. The striatum/cerebellum ratio of ¹¹C-clozapine-derived radioactivity remained constant during the period studied and did not change after pretreatment with atropine. In contrast, the striatum/cerebellum ratio was somewhat lower after pretreatment with N-methylspiperone (NMSP), indicating competition for the same binding sites in the striatum. After pretreatment with increasing doses of clozapine, a dose-dependent protection of binding sites in the striatum for ¹¹C-NMSP was seen. It is concluded that clozapine is more loosely bound to dopamine receptors in the striatum than N-methylspiperone and that the kinetics of clozapine in the brain parallel that in the plasma. The binding properties of clozapine within the brain may explain some of the clinical properties of the drug.     

HLA-DR7 predicts the response to alkylating agents in steroid-sensitive nephrotic syndrome

There is a lack of reliable predictors of the response to alkylating agents in children with idiopathic nephrotic syndrome (NS). HLA-DR7 is strongly associated with the frequency of relapses in steroid-sensitive NS before cytostatic therapy. We therefore examined retrospectively the time to the first relapse and the incidence of subsequent relapses in 54 HLA-typed children with frequently relapsing NS, after treatment with cyclophosphamide (n = 49) or chlorambucil (n = 5) for 8 or 12 weeks; 38 patients were HLA-DR7 positive and 16 negative with 80% in both groups being steroid dependent. HLA typing was performed using serological or DNA typing methods. Renal biopsy showed minimal glomerular changes. A lower proportion of HLA-DR7 positive than negative patients remained in remission after 3 years (36% vs. 81%, P<0.02) and 5 years (36% vs. 72%, P<0.03). In the first 3 years after cytostatic therapy the mean number of prednisone-treated relapses was 1.3/patient per year in HLA-DR7-positive patients compared with 0.4 in negative patients (P<0.025). There was no statistically significant difference in the proportion of relapse-free patients with and without steroid dependency. The HLA status predicts the response of NS patients to alkylating agents better than the rate of previous relapses. Received September 19, 1995; received in revised form and accepted April 16, 1996     

Urination Frequency and Cystic Pressure Resistance After Fractionated whole or Partial Irradiation of the Rabbit Urinary Bladder

Urination frequency and cystic pressure resistance have been used as end-points to assess x-ray-induced changes of bladder function. Whole or half bladders of adult male rabbits were irradiated, caudally or cranially. The absorbed dose was 33 Gy, 36 Gy or 39 Gy, given in 5 daily fractions. Animals which received a whole bladder dose of 39 Gy or 36 Gy showed increased urination frequency and enhanced bladder pressure resistance during the whole follow-up time of 100 weeks, compared with the sham-irradiated controls. At half bladder irradiation, only the highest doses (39 Gy to the cranial part of the bladder and 39 Gy or 36 Gy to the caudal part) gave rise to a slight increase in frequency at about 20 weeks after exposure.     

Cisplatinum Dose Dependent Response in Germ Cell Cancer Evaluated by Tumour Marker Modelling

This study presents an analysis on longitudinal tumour marker series in twenty-two patients with non-seminomatous germ cell cancers treated with cisplatinum (DDP) based combination chemotherapy. Series of alphafoetoprotein (AFP), human chorionic gonadotropin (HCG) and lactate dehydrogenase (LDH) were analyzed applying a dynamic mathematical marker model. The model analysis provided quantitated values for growth rate and treatment response in the marker producing cells. The analysis showed that LDH had to be above 2 000 U/l to be a trustworthy tumour marker. HCG producing cells tended to grow faster than AFP producing cells, and were 3-5-fold more sensitive to the chemotherapy given than AFP producing cells. Treatment response versus DDP dose appeared to be bi-phasic, but with no significant change in treatment efficiency within the given range of DDP doses.